Alternator circuit protector

ABSTRACT

A relay assembly having a coil connected between the terminals of a vehicle battery. The switch contacts of the relay assembly complete a connection between one of the battery terminals and ground when the coil is energized in response to the closing of an ignition switch. A diode is connected in the coil circuit to prevent the connection of the battery to ground if the battery is connected with the wrong polarity.

United States Patent Rollen et al.

[ 5] Mar. 7, 1972 ALTERNATOR CIRCUIT PROTECTOR Inventors: Wayne N.Rollen; Larry J. Strong; l-Inrschel H. Rolen, all of 80] East BakerStreet, Plant City, Fla. 33566 Filed: Mar. 20, 1970 Appl. No.: 2!,233

U.S.CL 307/ BP 1m. ..H02j 7/00 Field ofSenreh ..320/25. 26; 307/127,133, l0 BP,

References Cited UNITED STATES PATENTS 3,2l9,903 1l/l965Larson.....,..............4...............320/

3,300,702 l/l967 Noddin ..320/25 3,3l3,995 4/l967 Bach....... ...320/253,398,347 8/1968 Citro ..320/25 Primary ExaminerWilliam M. Shoop, Jr.Assistant Examiner-Harvey Fcndelman Attorney-Clarence A. O'Brien andHarvey B. Jacobson ABSTRACT 8 Claims, 1 Drawing Figure l a T l 23 1.- lALTERNATOR1l l REGULATOR! 22 T T T A a 1 /8 3a 36 fl T ACCESSORY CIRCUITl i fll h I2 34 ,0 l

L \h W 44 4e Patented March 7, 1972 3,648,146

l l 23 ALTERNATOR:-}: REGULATOR 22 LOAD TO IGN'T'ON ACCESSORY PT WayneN. Roi/en Larry J. Strong Hursche/ H. Ro/en Mm (Wavy 3m ALTERNATORCIRCUIT PROTECTOR The present invention relates to a relay assembly forpreventing damage to a vehicle alternator due to the connection of thebattery in circuit with the wrong polarity.

In the wiring system of many conventional vehicles, there is analternator which serves the purpose of recharging the vehicle battery.When the alternator is short circuited or destroyed by reverse polarityin the electrical system, it must be replaced at a considerable cost tothe vehicle owner.

The present invention seeks to remedy this problem by placing a relayassembly in the electrical system. The assembly includes a coil which isconnected in series with the battery and the ignition switch of avehicle. In order to ensure that current will flow through the circuitonly in response to a preselected polarity condition of the battery, adiode is also serially connected with the coil. During inoperativenessof the vehicle, the battery remains floating" which means that it is notconnected to ground. However, once the ignition switch is closed and thebattery was placed in circuit with the preselected polarity, switchcontacts in the relay assembly are closed to complete a connectionbetween ground and the battery so the recharging circuit of the vehicleelectrical system can operate as usual.

In order to permit use of vehicle electrical accessories, a bypasscircuit branch is connected across the relay assembly. The circuitbranch also includes a diode for conducting ground current through acircuit breaker protecting solid-state accessories against excessivecurrent at all times as well as polarity reversal.

A holding voltage must be applied to the coil in order to retainconnection between the battery and ground. Therefore, should a shortdevelop in the wiring harness, the holding voltage will not be generatedand the battery will be disconnected from ground. This monitoring ordetecting function serves to protect the electrical wiring from burningdue to a short in the harness. The present invention is inexpensive tofabricate and is simply installed in the main ground circuit of thevehicle electrical system.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawing forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

The FIGURE is a cross-sectional view illustrating the component parts ofa relay with the connected electrical circuit shown schematically.

Referring to the drawing, the present relay assembly generally indicatedby reference numeral serves to isolate a vehicle battery 11 from systemground until proper polarity of the battery is established in thecircuit and the vehicle ignition switch is turned on.

In the electrical circuit connected to the relay assembly 10, it will benoted that a negative ground system is indicated. However, if a positivegrounded system is to be employed, the principles of the presentinvention apply equally well, requiring only the changing of biasing ofcertain electrical components as will become evident hereinafter.

The positive terminal 12 of battery I1 is serially connected to aselector contact l4 of ignition switch [6. In a conventional electricalsystem, this switch contact is connected to a grounded alternatorthrough a connecting lead 18. A grounded regulator 22 is connected tothe alternator 20 through connecting lead 23 and serves to regulate theoutput DC voltage of the alternator. A connecting lead 24 extendsbetween the regulator and the contact 14 of ignition 16.

A first terminal or binding post 28 extends outwardly from the relayassembly [0 and serves to mount a lead 32 connected to the negativeterminal 30 of battery II. The terminal 28 is a first input terminalwhich electrically cooperates with a second input terminal 34, likewiseextending outwardly from the relay assembly 10. The second terminal 34is directly connected to the cathode 36 of a semiconductor diode 38. Theanode 40 of the diode is directly connected to the fixed contact 26 ofignition switch 16. Thus, with the ignition switch [6 closed, and withthe polarity of battery II connected in circuit as shown, current willbe caused to flow from the battery through the series circuit includingthe ignition switch 16, the diode 38, and the input terminals 28 and 34of the relay assembly 10. Once this electrical condition exists, therelay assembly 10 becomes actuated causing an internal connectionbetween input terminal 28 and an output terminal 42 directly connectedto ground 44. Thus, the input terminals of the relay assembly operateindependently of the system ground and when the relay assembly becomesactuated, the battery 11 ceases to be floating and the negative terminal30 of the battery is directly connected to ground. The internal relaycomponents for achieving this actuation and ground connection will bediscussed hereinafter.

Often, it is necessary or desirable to have the electrical accessoriesof a vehicle operating by closing the accessory switch 31 while theremaining electrical system is turned on. In order to achieve this endwith the present invention, ground for the accessory load 46 isconnected by a bypass circuit branch 48 across the input terminal 28 andthe output terminal 42 of the relay assembly 10 to the negative tenninal30 of the battery. This bypass branch includes a circuit breaker or fuse50 serially connected to the cathode 54 of a diode S2. The anode S6 ofthe diode is directly connected to the output terminal 42 of the relayassembly 10. Utilization of diode 52 guarantees that the accessorieswill not be connected to ground unless proper polarity exists. This isparticularly important for those electrical accessories utilizingsolid-state components extremely sensitive to reverse battery polarity.ln clusion of circuit breaker fuse 50 limits directionally correctcurrent flow to the accessories thereby preventing accessory burnoutunder all conditions.

As to the mechanical aspects of the relay assembly 10, reference numeral58 denotes a boxlike housing of insulating material which encloses thecomponent portions of the relay assembly. A hollowed cylindrical member60 is mounted at one end thereof to the interior surface of a housingwall by means of an integrally formed base 62 at the upper end of thecylindrical body as viewed in the figure. The opposite end of thecylindrical body is opened and receives the cylindrical portion of aplunger 64. The cylindrical body 60 is made from an insulating materialand serves as a journal or guide for plunger 64 which is fabricated froma ferromagnetic material. A coil spring 66 is located in the interiorspace of the cylindrical body 60 and normally urges the inward end ofplunger 64 outwardly so that approximately one-half the length of theplunger remains joumaled in the cylindrical body 60. The outward end ofplunger 64 terminates in a disclike contact 68 in tegrally connected tothe cylindrical main body of the plunger. The length of the cylindricalplunger body is such that the disc contact 68 abuts a confronting wallof the housing due to the biasing effect of the coil spring 66. Theinput terminal 28 extends inwardly to a cylindrical contact 70 generallyresembling the contact portion of plunger 64. The disc portion ofcontact 70 is disposed above the disc portion 68 of plunger 64.Likewise, the output terminal 42 includes a contact 72 extendinginwardly in aligned confronting relation with the contact 70 so thatwhen the disc portion 68 of plunger 64 is moved upwardly, an electricalconnection is made between the contacts 70 and 72 via contact 68.

In order to effect this upward displacement of contact 68 and itsattached plunger 64, a coil 74 is wrapped around the lower end portionof the cylindrical body 60. The coil 74 is positioned in outwardconcentric relation to the inward end portion of plunger 64 so thatmaximum magnetic linkage between the coil and the plunger is effected. Afirst end of coil 14 is indicated by 76 and is seen to be internallyconnected to the input terminal 34. The opposite end 78 of the coil isinternally connected to the other input terminal 28. Thus, the inputterminals 28 and 34 form terminals for the coil 74 which is energizedwhen the ignition switch 16 is closed. Energization of the coil causesupper axial displacement of plunger 64 until the aforementionedconnection between the contacts 68, 70 and 72 is effected. Once thiscontact is made, the negative terminal 30 of battery 11 is directlygrounded in bypass relation to diode 52. Likewise, actuation of therelay causes direct grounding of the accessory load 46.

During normal operation of a vehicle, a circuit is completed between thebattery I] and ground 44 so that the battery may undergo charging byalternator 20. When the ignition switch 16 is opened afier motorshutdown, coil 74 is deenergized to open the switch contacts 68, 70 and72 whereby the negative terminal 30 of battery 11 becomes isolated fromground by the diode 52. Of course, at a subsequent time, when theignition switch 16 is again closed, the operation of the relay assemblyis repeated as hereinbefore described. If the battery were connectedwith its terminals reversed, diode 40 would block flow of energizingcurrent to the coil 74 of relay assembly to prevent grounding of thebattery and hold the ignition circuit open to prevent engine operation.The accessory load would be protected by the diode 52.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

l. in combination with a charging circuit and a grounded load adapted tobe connected to one terminal of a DC source of potential having anotherterminal, protection means for the charging circuit and the loadcomprising ground circuit means adapted to be connected to said otherterminal of the source for limiting flow of ground current to maintainthe source in a substantially floating condition, polarity sensing meansconnected to the load for detecting flow of current thereto in onedirection, and switch means operatively connected to the polaritysensing means for shunting said ground circuit means to ground thesource at said other terminal.

2. The combination of claim I wherein said ground circuit means includesa diode and a fuse connected in series between said other terminal andground.

3. The combination of claim 2 wherein the polarity sensing meanscomprises a current responsive holding coil and a unidirectional currentconducting device connected in series across said terminals of thesource, said coil when energized holding the switch means closed.

4. The combination of claim 3 wherein said load is an ignition circuitconnected to the polarity sensing means and an ignition switchconnecting the sensing means to said one terminal of the source.

5. The combination of claim 5 including a grounded acces sory loadconnected to said ignition switch.

6. The combination of claim 1 wherein the polarity sensing meanscomprises a current responsive holding coil and a unidirectional currentconducting device connected in series across said terminals of thesource, said coil when energized holding the switch means closed.

7. The combination of claim 1 wherein said load is an ignition circuitconnected to the polarity sensing means and an ignition switchconnecting the sensing means to said one terminal of the source.

8. The combination of claim 7 including a grounded accessory loadconnected to said ignition switch.

1. In combination with a charging circuit and a grounded load adapted tobe connected to one terminal of a DC source of potential having anotherterminal, protection means for the charging circuit and the loadcomprising ground circuit means adapted to be connected to said otherterminal of the source for limiting flow of ground current to maintainthe source in a substantially floating condition, polarity sensing meansconnected to the load for detecting flow of current thereto in onedirection, and switch means operatively connected to the polaritysensing means for shunting said ground circuit means to ground thesource at said other terminal.
 2. The combination of claim 1 whereinsaid ground circuit means includes a diode and a fuse connected inseries between said other terminal and ground.
 3. The combination ofclaim 2 wherein the polarity sensing means comprises a currentresponsive holding coil and a unidirectional current conducting deviceconnected in series across said terminals of the source, said coil whenenergized holding the switch means closed.
 4. The combination of claim 3wherein said load is an ignition circuit connected to the polaritysensing means and an ignition switch connecting the sensing means tosaid one terminal of the source.
 5. The combination of claim 5 includinga grounded accessory load connected to said ignition switch.
 6. Thecombination of claim 1 wherein the polarity sensing means comprises acurrent responsive holding coil and a unidirectional current conductingdevice connected in series across said terminals of the source, saidcoil when energized holding the switch means closed.
 7. The combinationof claim 1 wherein said load is an ignition circuit connected to thepolarity sensing means and an ignition switch connecting the sensingmeans to said one terminal of the source.
 8. The combination of claim 7including a grounded accessory load connected to said ignition switch.